Here is how to defrag the index:
https://support.microsoft.com/en-us/kb/2838018
But, the size issue is, as of now, unsolvable and Microsoft recommends it not be used on 2012 R2:
https://social.technet.microsoft.com/Forums/windows/en-US/33d554bd-cd33-4869-9fc7-73b3ec835039/windows-search-edb-file-very-large-on-server-2012-r2-rds?forum=winserverTS

I agree with David above. The best I would suggest is if you really must use it on RDS, enable it and monitor the EDB file, and when it gets to a threshold, turn it off, which I believe deletes the EDB, but if not, just do it yourself, and then re-enable it.

There is a long-ish article that details compacting it or defragging it when it gets to big:

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